What is a wetland?A wetland is an area of permanently orintermittently wet land and shallow water, withfluctuating land-water margins. Wetlands may befresh, saline or a mixture of both, and arecharacterised in their natural state by plants oranimals adapted to living in wet conditions. Theyare unique habitats for many such species.

Wetlands on farms encompass a variety ofwaterbodies and landforms - a coastal salt-marsh ormangrove swamp; a freshwater lagoon; boggyseepages; wet margins of a lake, river, stream ordrain; a peat bog; and even a stock water dam oreffluent pond. They stand out in the landscape,with outlines etched sharply by a dramatic changein vegetation.

As there are few unmodified or undrained wetlandsremaining in Taranaki, the Regional Councilencourages landowners to preserve existingwetlands on their properties. Rules in the RegionalFresh Water Plan control drainage that affects thesignificant wetlands listed in the plan. A resourceconsent is also required for land drainage thataffects any wetland greater than five hectares.

Wetland management should be viewed as anintegral component of sustainable landmanagement.

Wetland functions & valuesWater StorageWetlands store water and during times of rainfalland flood slowly release it to downstream areas,lowering flood peaks. They also provide a reservoirof water for release during dry periods. In doing so,they help maintain base flows in streams andprovide aquifers with an opportunity to recharge.

Erosion & sediment controlIn reducing flood flows and the velocity offloodwaters, wetlands reduce erosion and allowfloodwater to drop its sediment. Wetland vegetationfilters and traps sediment that would otherwiseenter watercourses, lakes, ponds and the ocean. Thishelps preserve the quality of inland and offshorefisheries, such as those for whitebait or inanga, theshort-finned eel and estuarine flounder.

Pollution prevention & controlWetland vegetation intercepts nutrients, sediment,and organic matter in slow-moving water, whilemicro-organisms utilise it and break it down.Runoff emerging from a wetland is typically muchcleaner than when it enters. Wetlands, both naturaland man-made, assist to extract nitrogen andphosphorus from farmland runoff. They are nowincreasingly used for tertiary treatment ofagricultural and industrial effluents.

Habitat for indigenous speciesThe land-water interface is among the richestecosystems in the world. Many plants and animalsare especially adapted to live in wetland conditions.The survival of a diversity of plant and animal life,including rare species, is threatened as many of ourwetlands, particularly swamps, have been clearedand drained.

RecreationWetlands, particularly lakes, are important forfishing, duck shooting, boating, swimming, birdwatching and other forms of outdoor recreation.

Figure 1: A wetland has multiple functionsand many values

Wetlands

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Other valuesIn addition to the above functions, wetlands alsopossess educational, scientific, cultural and scenicvalue. Wetlands offer study areas for ecology andbiology. They are a source of information on historicclimate and vegetation, and are a scenic part of thenatural landscape. In addition, they are important toMaori as mahinga kai (food gathering areas) and area source of plants for medicines and dyes. Theywere used to store tribal artefacts and remainresting-places for these taonga or treasures.

Wetland managementThe best form of management for a completelynatural wetland might simply be to fence it and thenleave it alone to look after itself. However, suchunmodified ecosystems are rare and in most cases, anatural wetland area on a farm needs activerestoration and manipulation of all its components -water level, plants and animals. The followinginformation describes some of the considerations;more detail can be found in the Department ofConservation’s publication New Zealand's Wetlands- a Management Guide.

Buffer zonesA buffer zone protects a wetland from outsideinfluences and is generally a strip of land betweenthe outer wetland fringe and the adjacent land. Itprotects the wetland from outside influences such asgrazing and runoff, as well as providing a refugefor birds, fish and other wildlife. A buffer zone isparticularly important to the survival of small orsensitive wetlands. Stock access should berestricted, if not completely excluded.

The width and nature of a buffer zone depends onthe purpose for which the zone is to be used. If it isto filter runoff, it needs to be a wide well-grassedstrip of land. A buffer which is used as a visualscreen does not need to be quite so wide, and can beplanted with trees and shrubs. At the very least,any banks or steep slopes next to the wetland shouldhave a narrow strip of protective vegetation. Anyinlets and outlets should also have buffer zones.Make sure that the outline of the buffer zone followsthe natural shape of the wetland and the contours ofthe land i.e. not square or straight; otherwise itsvisual appeal will be lost.

Control of grazingFencing should be sufficient to protect the wetlandfrom unplanned grazing. Fences should be wellconstructed, and of high quality. A conventionaleight-wire fence or a five-wire electric fence is ideal,however not always practical. The most practicalsolution depends on the farming system and type ofstock. A permanent 2 wire electric fence may beadequate on a dairy farm. See the Council's

information sheet Riparian Fences for severalalternative designs.

Stock can cause erosion, trampling and pugging ofsoft ground in a wetland. They eat and trampledesirable plants, introduce unwanted weeds, disturbwildlife and create high concentrations of nutrientsby voiding dung and urine.

The level of grazing, if any, will depend on thereasons for which the wetland is being managed.For instance, a few open areas within the buffer zoneare desirable for waterfowl, and low level grazingwould achieve this. Light sheep grazing ispreferable to heavy grazing by cattle.

Grazing, however, should cease or be significantlyreduced one month prior to the breeding season forbirds. It should definitely cease during the breedingseason. Similarly, in areas where fish spawn, itshould cease during the time they are spawning.Generally, the most sensitive months for wildlife areOctober to December.

Water Level ControlNatural fluctuations in water level are a feature ofwetlands. Some species adapt to the fluctuationswhich may provide additional food sources oractivate breeding stages in fish, birds and insects. Itis important that these natural water fluctuations aremaintained, as unnatural water levels can adverselyaffect plant growth and animal reproduction.

In situations where natural fluctuations in waterlevel can no longer occur because of outsideinfluences such as dams deliberate raising orlowering of the level may retain some of thewetland's values. Consult the Taranaki RegionalCouncil if planning to undertake any drainage ordamming near a wetland, as these activities mayrequire a resource consent.

Drainage or reclamation, diversion of water out of,or discharge of contaminants into regionallysignificant wetlands (listed in the RegionalFreshwater Plan) is in some cases discretionary andin others prohibited.

Figure 2: Adequate fencing is an important stepin protecting wetlands.

A resource consent is required for drainage nearother wetlands, if the area being drained exceeds 25ha.; or if significant flooding, scour erosion ordeposition may result; or if there may be significantadverse effects on aquatic life and habitat.

Land use outside the wetland can and will affect thewetland itself. Where possible, altering drainage in awetland or immediately outside a wetland shouldbe avoided. Side-effects should be assessed beforeundertaking drainage and precautions put in placeto minimise them.

Precautions must also be taken when cleaningdrains. Drains should be cleared in stages tominimise harmful effects (excess sediment loads,disturbance of fish habitat). Avoid deepeningdrains when cleaning them, as this may over-drainthe wetland.

Fish accessWetlands are habitat for native fish, notably galaxidspecies (whitebait) and eels. If the wetland isconnected to a stream or drain which is used as afish migration pathway, make sure that the inletsand outlets allow fish access to and from thewetland. For instance, culverts should not dischargewater from a height into a streambed, but rathershould be partially submerged so that there is nodrop below. For further information on designingand developing appropriate structures and fishpasses, contact the Taranaki Regional Council or theTaranaki Fish & Game Council.

Avoid introducing exotic fish species into naturalwetlands - some, such as grass carp, displace nativefish from their habitat; others like mosquito fishattack and kill them.

Enhancing habitat for birdsArtificial nesting sites may increase bird numbers inwetlands by encouraging breeding and providingprotection from predators. Islands can providepermanent nesting sites - just about any material canbe used for an island so long as it will notcontaminate water, sits just above the water leveland is easily covered with sufficient soil to supportplants. Rafts are alternatives to islands in deeperwater or where water levels fluctuate markedly.Again, they can be made of any durable material butshould be secured at both ends to prevent themswinging in the wind.

Trees, stumps and old posts protruding from openwater can provide important nesting and loafingsites for birds such as kingfisher and heron. Wherebirds do not have the specific materials for buildingnests, nesting boxes can be built to encouragebreeding.

Figure 3: Koaro (Galaxias brevipinnis)

It is important to leave a stretch of pond margin freeof taller vegetation, as birds like access to land forresting, mating and breeding.

In time, natural nesting sites of waterfowl will beginto develop as wetland vegetation increases.However, it is important to ensure that the wetlandis capable of supporting the increasing birdlife.

The most common waterfowl in the district are theparadise shelduck, mallard, and grey duck.Paradise ducks principally feed on pasture and usewetlands as `loafing' sites, evening refuges, andsometimes to raise their young. Mallards and greyducks tend to make wetlands their home. They feedin the shallow water and on the muddy shores.The submerged plant zone is suited to the shoveler,swan and New Zealand's only diving duck, thescaup. The shoveler is able to sift plankton and seedwith its large bill, which is surrounded by a finesieve-like structure. The swan's long neck enables itto feed on submerged roots and plants, while thescaup grazes on invertebrate life and shifts bottomsediments.

Planting in wetlandsA wetland can be divided into different zones -dryland, marginal, emergent and submerged (Fig 4).Different plants survive in each zone, so whenrestoring wetland vegetation, it's important tochoose the right species.

Depending on the type of wetland, and itsrestoration or management requirements, plantingsin each zone may not always be needed. Plantingsome zones may not be feasible. A simpleapproach can often be implemented to suit thepracticalities of each situation.

Dryland zone At the outer edge of the wetland are dryland plantassociations which can include grassland, scrublandand forest trees such as kahikatea. Although theplants in this zone encounter and survive sporadicflooding, the water table is generally below groundlevel. The plants themselves provide shelter from

Figure 4: Wetland plant zones

cold winds, shading and cover for fish, andprotection from predators.

Marginal zoneWithin the area of the water's edge are marginalplants such as rushes, sedges, raupo and flax. Theseplants can survive prolonged periods of floodingand drought. Marginal vegetation easily establishesitself in new habitats.

Emergent zoneWithin permanent shallow water, emergent plantssuch as pond weed and watercress grow withsubmerged roots and stems, but require their leavesto be exposed for oxygen transfer. Floating plantssuch as waterfern and duckweed are also regardedas emergent plants. Emergent plants can surviveshort periods of total immersion or exposure, but arerare in unsheltered open water because ofturbulence from waves.

Submerged zoneIn deep water such as pond bottoms andstreambeds, submerged plants such as stonewortand quillwort are completely covered with water formost of the time. The extent to which these plantsoccur depends on the substrate, light, chemical andbiological conditions prevailing in deep parts of thewetland.

Guidelines for planting• Refer to the Council's information sheet

Establishing Riparian Vegetation for details ofplanting techniques. Some additionalguidelines, specific to wetlands, are :

• Blend in plantings with the natural features• For a more natural effect, plant groups of 3 to 5

trees and shrubs in groups i.e. not a straight line

• Avoid planting the wetland margin completely.This impedes the natural flight path ofwaterfowl

• Use low growing species near the water's edge,with occasional tall trees over hanging the waterand some gaps to provide waterfowl withescape cover

• Select a variety of plants that will provide acontinuous food source around the wetland

• The wetland should be visually attractive -consider the mix of plant species; tall and short,deciduous and evergreen, flowering and non-flowering, and colour for all seasons

• Where possible, source plants from the localdistrict, as they will establish more easily

• If an area has been dammed, do not plant thedam wall. The roots seek the nearest water andbecome seepage channels, weakening the wall

• Do not plant pampas grass or similar dense-growing species. These plants act as havens forrats, ferrets, weasels, and possums. All aredestructive to the wetland wildlife or vegetation

• It may be necessary or desirable to controlplants which are not wanted or which invadewetlands - examples are gorse, broom, willows,spartina and water hyacinth. In some places,even native wetland plants can be a problem.For example, raupo tends to crowd out otherplants. Control is probably more practical thantotal eradication, and should be carried out inautumn to minimise damage to wildlife anddesirable plants.

For more information please contact:The Land Management Section,Taranaki Regional Council,Private Bag 713, StratfordPh: 06 765 7127 Fax: 06 765 5097www.taranakiplants.net.nz